Electrical converting apparatus



Jan. 7, 1941. R. u.' CLARK ELECTRICAL CONVERTING APPARATUS Filed Oct. 14, 1938 ATTORNEY.

Patented Jan. 7, 1941 I UNITED STATES- PATENT OFFICE ELECTRICAL CONVERTING APPARATUS v Richard U. Clark, Fort Wayne, Ind. Application October 14, 1938, Serial No. 235,086

8 Claims.

The present invention relates to electrical converting apparatus and particularly to circuits used-in conjunction with electron discharge tubes and their associate equipment when employed a for the purpose of converting direct current into alternating current, or pulsating current, or in converting from one voltage of direct current to a higher or lower voltage of the same.

Among the objects of the present invention 10 is to provide an electrical conversion circuit in which the electron discharge tubesto be assoelated therewith are caused to oscillate at a fairly constant frequency regardless of the amount or nature of the out-put load supplied 10 by the converter; also to provide a conversion circuit adapted to give good'regulation of output load voltage regardless oi the nature or amount of the load; as well as to provide a circuit which incorporates a suitable time delay 20 device ior applying the plate voltage to the inverter tubes. v Further comprehended within my invention is a circuit which is 'nonstalling and self starting in the event of partial stalling: to provide a new 25 means for deriving cathode heating power from the inverter circuit without the need of adding extra. parts and an improved automatically controlled method of making and breaking the discharge current through the electron discharge tube or tube sections which is particularly adapted for use in electron discharge tubes such as described and covered in Patents No. 2,130,380 and Reissue No. 20,727 issued to the present w r attempts have been made in the past to devise inversion circuits for use with vapor electric tubes for changing direct cu'rrent to alternating current but all of the circuits heretofore brought forth in the form of parallel inverters have had the common failing that they may; stall or fail through over-load or minimum ,load conditions. and when so stalled, are no longer self-starting.

en such inverters stall a high current are 45 forms and often ruins the electron tube cathodes and even where expensive circuit breakers are used to prevent high current arcs there is no guaranty that they may notjail to work. Also they do not help in any way to correct the fault or stalling cause.

In the series type of inverter there is generally less danger that stalling will take place than in the parallel type, but here again a sac riiice in efficiency is made as the energy loss 65 due to the required use of two separate cathodes coil 82 being one conventional form of arranE- is considerable. There is also a tendency for commutation to fail at light loads causing the inverter to stall.

In addition to the foregoing no practical circuits of the series type have been heretofore 5 devised for low voltage operation, nor has any simple circuit which embodies fault correctio been heretofore known.

Another inefliciency common to many prior types of inverters is that they incorporate grid phase control systems for starting of the arc and condenser assisting means for extinguishing the arc and these circuits are claimed to operate purposely under other than resonance conditions.

In the present circuit, operation is had atits resonant frequency. When correction of faults is taking place and under no load conditions, the natural period of the circuit may however change due to the automatic action of the correcting agency. The timing of the grid plate voltage relation once the inverter is started is obtained in the present invention by the com bin'ed action oi coupling of the grid transformer to the platecircuit plus periodic rise and fall in voltage of the center point on the in-put side of the circuit which fluctuates in voltage in unison with each pulse through the inverter tubes 4. or tube sections. This point on the in-put which supplies the fluctuating voltage is so devised as to give automatic control or frequency.

Further objects and advantages of the present invention will become apparent upon consideration of the circuit shown in the accompanying drawing. 1

The drawing, for illustrative purposes and not as limiting my invention. shows diagrammatical- 1y one form of"ciro'uit for carrying out the present invention, and in longitudinal section an electron discharge tube connected therewith.

Referring to the drawing, ior simplicity, the 40 a direct current input is shown as a hattery connected to'switch i5 audit-a. The alternating or pulsating power output of the device may take several conventional forms; the inductive ing output connections. There is shown an electron discharge tube I having a common cathode 2, grids 3 and 4 connected to leadsr or conductors l and l, and

' plates or anodes 5 and 6 connected to suitable 59 leads or conductors 5' and 8'. A center tapped inductance I having a center connection at point I connects at one end to plate I and the other end to plate 8. Connected to point Sis a speclal ballastresistance device 8 having elements -,Shunting condenser 30 and 3!. Element 2| connects to point I at one end and to a small inductance II at the other end. There is also an inductance l I used in conjunction with inductance 'II in the plate circuit. These two inductances have a common connection through a thermal relay i2, which in turn connects into the tank condenser IS, the remaining terminal of which is connected to the normally positive end of the cathode, or cathode heater, or heaters through conductor vl4. The plate voltage in-put SHDDLV. shown as a battery, connects to inductance ll through switch i5, which switch is also made as a part of, and lS-a. The plate battery's negative terminal I 6 connects through an isolation inductance id to the positive cathode terminal of the tube and also to the positive of the cathode battery, which may be common with the plate batery, and whose negative terminal in turn connects with the oathode of the tube through conductor ll.

The plate tuning condenser i! and the primary of the grid transformer-2U are connected in series and across the two anode conductors i and i. 'I'he outside secondary terminals of the grid transformer 20 are connected to the tube grids through conductors? and 4'. The center tap 28 of the grid transformer secondary is connected to resistor 2i and one terminal to condenser 22. The remaining terminals 01' resistor 2| and condenser 22 are connected to the Junetion of the condenser 24 l3 are resistors (optionally inductive) 25 and 26. Condenser 21 is connected in parallel with resistor 26. Resistor 23 connects to the common junction of 25, 26 and 21. Said junction is joined also to one terminal of the ballast resistor 3i. Resistor 3| is connected to condenser 24 at its remaining termina1.

To start the inverter shown in the drawing..

operating switch l5l5 --a is closed. This sure plies electric energy to cathode 2 and supplies plate voltage to the tube anodes through (normally. closed) thermal switch 12. Condenser I3, which is of high capaci say 200 microfarads, immediately starts to charge, drawing a momentary high current surge from the plate battery. This charging surge heats the thermal element of relay l2, temporarily opening the plate circuit which is common to both tube anodes. By the time the thermal relay it cools sufliciently to close, the tube cathode is heated and emission started. Simultaneously periodic electrical oscillation is started by virtue of the tuned coupling of transformer 26 between. the Plate and grid circuits oi the tube. For the short initial period during which relay i2 is closed, no appreciable plate current flows since the cathode is cold. In the tube cathode is hot from turned on, plate current of short duration may flow, but not sufficiently long to damage the cathode before 'relay l2 opens. Subsequently upon the automatic re-closing of relay i2, the device will start in the normal manner.

When the thermal switch l2 closes the second time in starting, the potential of both grids is boosted by the action of choke ll, condenser i3, transformer 20 and the inter-connected resistance network, and because of slight diiferences in grid control ratios, naturally inherent in the 'tube structure, one circuit through the tube willionize .and fire before the other and from this point on both sections of the tube will ionize and continue to oscillate as a conventional previous use when directly connected to, filament switch and the resistor 23.-

. previously,

shunts, and condenser event the inverter coupled oscillator, except that the grid potential for initiating ionizatiomas desired, is timed by the voltage surges across 25 and 21, which surges originate across the direct current in-put choke and are transmitted to condenser l3 and its associate network.

Undulating voltage waves are generated as follows: with circuit excited by D. 0., current flows to the tube plates with alternating conduction through the two sections, (plate to cathode section), of tube, causing acyclic rise and fall oi current through series inductances in the inpp y- The reason for voltage across-condenser I3 is due to the passage of undulating current through condenser 13. The frequency of this undulating current and voltage tends to vary slightly as the output load ofthe inverter is changed. When the load is increased the inverter input must supply more current to take care of the demands of the increased load which 01' course lowers the input inductances due to the tendency to short circuiting eiTect. As the inverter strives to draw more current which must be passed through the input, the input inductances pass more steady D. C. and .with the lowered efiective inductance due to approaching saturation, tends to cut down the amplitude of the variable current through the inductances and therefore the amplitude of the voltage across the condenser i3. The resulting tendency from this lowering of impedance is to increase the frequency of oscillation of the inverter but the concurrent risein resistance due to the additional current passing through the thermal exchange resistor 9 through its coil or filament 30 .raises the temperature of 30 and also 3!. 3!

property of decreasing in value when having the heated, tends to increase the effective capacity of condenser 24 by lowering its effective series resistance, thereby tending to tune the grid transformer secondary to a lower frequency than thus causing a fair degree of size.- bilization. In other words this prevents the frequency from changing materially, oi the system as a whole.

The grid circuit tuning condenser 25 operates in conjunction with condenser 22 although condenser 24' is chosen of a value such as to tune the grid transforme both halves of which it 22 affords chiefly a. bypass action. Condenser 23 tunes because of variations in resistor 3| in series withit.

Inasmuch as the grid control timing of the tube is related to resistors 25 and 28, it is obvious that a particular variation in grid timing may cult as the occasion-demands. Regulation is I also wish to point out that it is possible to partly from A. C.'fed through II to indirect cathvary the constants of the circuit described to ode heater. For directly heated cathodes this automatically correct overload conditions to a A. C.-may berectifled; high predetermined level without wide power Another important feature of this inventioniis' fluctuations in the output. l the method employed for utilizing electrical en Having thus described my invention I claim: 15 ergy from the input circuit to assist in energiz- 1. In combination in an electronic converter. ing the cathode heating element r'elements of a tube having plates and grids, inductances conthe tube, thus preventing, under ll ht or no load necting the plates, plate in-put means combinconditions, stalling or the inoperative condition ing two plate connecting inductances to an elecwhich results in conventional circuits. The A. C. trical in-put supply, a thermal relay interconcomponent through condenser l3 prevents this. necting said two inductors, a tube cathode, a constalling is overcome in the present circuit denser, means for initially charging the conthrough the use of energy available in the condenser through the relay and disconnecting the denser It. This condenser, in addition to its plate source from tile plates and automatically efiect upon the thermal relayand the grid timing reconnecting the same when the tube cathode is circuit, also supplies energy to the cathode, in heated to emitting temperature, a grid tuning inverse proportion to the load through the posinetwork, and a thermal exchange resistance contive leg of the cathode of the heater in the tube. r l device n series h h la e s pply n The largest amount of energy exists across the the operation thereof in series with the grid condenser II when the output load is small, and tunin ne workvice versa. Henc by utilizing a properly pro- 2. In combination in an electronic converter, portioned cathode heating element with this cira tu e h v p ates and ids. an indu tan cult, suiflcient cathode energy is supplied by connecting the Plates thereof. id o Pl 1- condenser ll during light load operation to pre- Flin m n Plate ill-P m induc n vent excessive discharge ofthe cathode battery. connecting h plates to an el ric l i -put uD- Likewise when the circuit i o erating und ply, a thermal relay interconnecting the inductheavy load conditions, the heating eilect of the ant s. n nser. a c thode, a condenser to plate current may be made to equal or exceed the cathode connection to said relay, means for cathode cooling eilect. Therefore, regardless of chargin the condenser through the relay a the load, thecathodebattery is not excessively p rar y disconnecting t e plates o the so drained. By virtue of the foregoing, the only plate in-put, said last named means automatiexcess energy drawn from the cathode section of tally nnecting the plat and Plate np the battery is drawn during the short period r when the cathode is heated to emitting temquired for starting, and due to the limited perature, a grid tuning network across the inamount of energy thus consumed, no separate but s p y and connectin e h h nbattery or battery charging"connections are red r d ing en and m l quired as is the case in conventional inverters. x h n e resistance control device in series with As a further improvement in controlling th the plate in-put, the operation of the thermal frequencyoi the alternating current output of my exchange resistance control device being in seinverter, I provide a-bulb I in, which s um m ries with the grid tuning condenser.

proportion to the plate load. I inductances connecting said plates to an elec- Material with anegative coefiicient-of resisttrlcal -P pply. a thermal relay in rconance is chosen for resistor 3| and since this renecting id two nducta ce a d e a sistor is in the grid circuit of the tube it will cathode, a condenser to cathode connection to follow if the output losd'in the plate c r uit said relay, means for initially charging said concreases, the filament llwill radiate more heat to denser through the relay thereby temporarily to resistor ll, causing a reduction in grid loss and disconnecting the plate in-put means from theproviding greater outputcapabilities inthe plate plates, and automatically reconnecting same andoutput circi'iit; when the cathode is heated to emitting temper- Material having a high positive coeilicient of ature', a grid tuning network, and a thermal exresistance is selected for the ballast filament as change resistance control in series with the plate so as to prevent oscillation failure throughp, in-put supply, so as to provide a converter cir-- p wer output overloads- Since the'fllament 8| is cuit stable in ope at 8 desired requency.. in series with the plate batterina sudden overwhich-will feed energy from the plate in-put to load will'result inarapid temperature rise in the V the cathode circuit durin op mtion. and D nlament, hence. an increase in resistance to a vent stalling dueto incorrect loading. 7o point-where oscillation will automatically start. 4. A parallel electronic converter comprising a Under normal operating conditions, equilibrium dual vapor electric tube, a tuned inductance conbetween the grid and plate circuits is thus quick-, necting the plates thereof. grid to plate cou- 1y established and maintained. l pllng means, plate input means combining two the tube is "causing the fluctuating voltage. which is applied It is evident from the foregoing that having a high negative ooeflicient of resistance. its instantaneous resistance value can be made to increase in proportion to the instantaneous drop in the ripple voltage across the condenser ll. thus.

and the associated inverter circuit will continue operation under both extremely light and excessively heavy loads. However, when either of these two' conditions exists beyond normal operating ranges, there will be power fluctuations in the output circuit and corresponding fluctuations in the ionization paths of the tube. Hence, the device will give visual indication of improper operating conditions.

to the grids" of the tube, to change phase providing frequency stabilization and longerconduction between the anode and cathode, which will supply the increased power drawn in the output cir- 3. In combination in an electronic converter, a dual vapor electric tube. a tuned inductance connecting the plates thereof, grid to plate coument 3. and resistor ii are thermally associated. Since filament II is in series with the plate circuit of the tube, it will follow that the filament will emit and transfer heat to the resistor II in inductances. connecting said plates to anelecpling means, plate in-put means combining two trical'in-put supply. a thermal relay interconnecting said two inductors, a condenser to cathode connection to said relay, means for initially charging said condenser through said relay thereby temporarily disconnecting said plate source from said plates, and automatically reconnecting same when said tube cathode is heated to emitting temperature, combined with a grid tuning network across said in-put supply to cathode condenser, and a thermal exchange resistance control device. in series with said plate supply and the operation thereof in series with a grid tuning condenser, suitable starting switches associated with said circuit, the foregoing means associating to provide a converter circuit which will operate stably at a desired frequency, which will feed energy from the plate in-put to the cathode circuit during operation and which will prevent failure or stalling due to incorrect loading of the out-put system.

5. In combination'in an electronic converter,

a tube having plates and grids, inductances connecting the plates. plate in-p'ut means combining two plate connecting inductances to an elec- .said' plates and said cathode, means coupling 7 saidplates and grids for causing current to flow irom said cathode to each of said plates respectively, a plurality of inductances in series in said connection whereby input fluctuation will appear betweensaid inductances, a condenser connected between a point between said inductances and terminal or said cathode, and means for connect- 5 ing the other terminal of said cathode to said source whereby said input fluctuations will ini tially excite said cathode and continuously maintain it at an eiiective emitting temperature.

7. In an electrical converter, an electronic tube 10 including an anode, cathode and grid, a connection including a source or potential between said anode and cathode, means coupling said anode and vcathode for causing current variations through the tube at a desired operating irequency, said means including a grid tuning condenser and a resistance which becomes less asits temperature is raised in series therewith, and

means for stabilizing the generating frequency comprising a heating means connected in series in said connection, said last named resistance being exposed to heating by said heating means.

8. In an electrical converter, an electronic tube including an anode, cathode and grid electrode, means for coupling said anode and grid forcausing variations in current in said tube at a desired operating frequency. a connection between said anode and cathode including a source of potential, and a plurality of inductances, an input condenser connected between said cathode and a point between said inductances, and means for utilizing the ripple voltage across the input condenser due to its said connections for timing the said current comprising an impedance across said input condenser and means for coupling 38 said impedance to said grid.

RICHARD U. CLARK. 

